Robotic parallel gripper assemblies mounted on robot arm assemblies are used extensively in industrial assembly line applications to grip, pick up and stack mass produced products. For example, one type of parallel gripper assembly is known as a bag gripper. The bag gripper typically has a pair of parallel booms with a plurality of fingers (i.e., the grippers) clamped to the booms. The gripper assembly controls the movement of the booms and fingers. The fingers are bent at right angles and are operable to pick up bags of product, such as mulch, garden rocks, sugar, cement, dog food or the like. The bag gripper will then stack the product on pallets for shipping. Another type of parallel gripper assembly is known as a box gripper. The box gripper will have paddles, instead of fingers, attached to the parallel booms. The paddles are operable to pick up multiple boxes and stack the boxes on pallets for shipping.
The distance between the pair of parallel booms can be adjusted and locked in place in order to accommodate different sizes and weights of products. For example, the booms may be rigidly attached to metal arms and the metal arms may be rigidly attached to clamping mechanisms for controlling movement of the booms and grippers. The clamping mechanisms may, in turn, be rigidly attached to mounting plates that slide on rails attached to a frame of the parallel gripper assembly. Therefore, movement of the metal plates along the rails will adjust the distance between the parallel booms. Once the mounting plates are adjusted, they can be locked in place with, for example, hand tools that bolt or clamp the mounting plates down.
The distance between the booms is critical. If the booms are too far apart, the grippers may not be able to consistently pick up the product from the assembly line. If the booms are too close, the grippers could damage the product. Therefore, once the booms are adjusted, the locking mechanism must be able to rigidly hold the booms in position during operation.
Problematically, during operation, parallel grippers are subjected to a great deal of vibration that can eventually loosen the prior art locking mechanisms and cause the booms to shift. This is due, in large part, to the repetitious nature of the parallel gripper's operation, as well as the weight of the products being stacked. For example, the product being lifted off of an assembly line and palletized can easily be in the range of 50 to 100 pounds in weight, and may be stacked at the rate of once every two seconds for tens of thousands of cycles per day.
Once the booms have shifted, product may be damaged and the production line may have to be shut down in order to re-adjust and re-clamp the booms. Further, the use of hand tools to adjust and clamp the booms can be time consuming and labor intensive.
Accordingly, there is a need for a mechanism to adjust the distance between booms of a parallel gripper assembly without the use of hand tools. Also there is a need for a locking mechanism for locking the booms into position that is largely unaffected by constant vibrations during operation. As such, the locking mechanism would be easier to operate and less susceptible to unlocking and shifting during operation of the parallel gripper.